Coal liquefaction energy efficiency

[leadraven]

I wondered what is more effective in terms of steam power : to burn coal OR to liquefy coal and burn solid fuel. Without modules.
I have found the fillowing math (and it's pretty fair):

Liquefaction input:
10 Coal * 8MJ = 80MJ
50 Steam * 30KJ * 2 (Boiler [in]efficiency) = 3MJ

Liquefaction output:
10 Heavy -> 7.5 Light
15 + 7.5 = 22.5 Light -> 2.25 Fuel
20 Gas -> 1 Fuel
Total is 3.25 Fuel * 25MJ = 81.25MJ

Output doesn't compensate even input materials, without calculating factories power consumption.

But now magic/logic comes.
I am sure that on your main oil factory you are cracking light oil into gas. And now, after liquefaction, you are making fuel out of gas. It's very inefficient. Instead of that let's safe gas from liquefaction and crack less light oil to keep same net gas output. 1 liquefaction cycle gives 20 gas what saves us 30 light oil.

New math:
10 Heavy -> 7.5 Light
15 + 7.5 + 30 = 52.5 Light -> 5.25 Fuel
5.25 Fuel * 25 MJ = 131.25MJ

Factories power consumption per 1 liquefaction cycle (it's not much but let's do it):
Refinery : 0.434MW * 5s/1 = 2.17MJ
Heavy cracking : 0.217MW * 3s/1.25 * 10/40 = 0.1302MJ
Fuel making : 0.217MW * 3s/1.25 * 52.5/10 = 2.7342MJ
NOT cracking Light oil : -0.217MW * 3s/1.25 * 20/20 = -0.5208MJ

TOTAL : 131.25 + 0.5208 - 83 - 2.17 - 0.1302 - 2.7342 = 43.7364MJ
We've got ~50% more energy with the same net output! The only condition is that you are cracking light oil. And I'm sure you do.

I hope everything is correct.
Fill your boilers with solid fuel, my bruddas!


UPD. And here is a little error. All energy consumptions shoud be doubled due to boilers. Correct total energy income is 39.2228MJ (fuel, not electricity). Still ~50%.

[quinor]

Add modules (efficiency, speed, productivity? probably prod + speed) and you get much more than +50%. Just saying!

[bobucles]

Your math is WAY off. Coal cracking produces +10Heavy, +15Light and +20Gas. Refineries also consume a non trivial amount of energy to function which makes modules very difficult to profit from. Behold:

Refinery: 420kW * 5 seconds * 2x inefficiency => 4.200MJ raw coal
Steam : 50 steam * 150C * 0.2kJ/C * 2x inefficiency => 3.000MJ raw coal
10 coal : 80MJ raw coal
Solid fuel: 210kW * 3 seconds / 1.25 production speed * 2x inefficiency => 1.01MJ raw coal tax on every solid fuel produced.

15 Light Oil => 1.5 Solid fuel => 25MJ * 1.5x =>37.5MJ raw coal
10 Heavy oil => 0.5 Solid fuel => 12.5MJ raw coal
10 Heavy oil => 7.5 Light oil => 0.75 Solid fuel => 18.75MJ raw coal (plus cracking tax of 252kJ raw coal)
20 gas => 1.0 Solid fuel => 25MJ raw coal.

So let's add it up.
37.5MJ + 18.75MJ + 25MJ => 81.2MJ recovered
81.2MJ/25 => 3.25 solid fuel recipes * 1.01MJ tax => 3.28MJ tax
80MJ + 3MJ + 4.2MJ + 0.252 MJ + 3.28MJ => 90.7MJ expenses

There's no point in using coal liquefaction for energy. A perfect -80% efficiency setup will bring your expenses down to 84.5MJ, which is still losing. You can try using productivity modules but the extra energy expense will almost certainly outpace any extra solid fuel you produce.

You will never come out ahead. Burn raw coal at all times. Don't use coal cracking for anything else than direct use of heavy oil or direct conversion to petrol. If you need extra petrol, the most resource effective priority is to crack ALL your existing oil and burn 100% coal and only crack surplus coal to make more petrol.

Edit: Rechecking taxes again. Yes, you can't have .25 of a solid fuel but when the recipe runs a few thousand times it all smooths out.

[leadraven]

15 Light Oil => 1.5 Solid fuel => 25MJ * 1.5x =>37.5MJ raw coal
10 Heavy oil => 0.5 Solid fuel => 12.5MJ raw coal
10 Heavy oil => 7.5 Light oil => 0.75 Solid fuel => 18.75MJ raw coal (plus cracking tax of 252kJ raw coal)
20 gas => 1.0 Solid fuel => 25MJ raw coal.

Did you read my post to the end?
You are pointing the same thing as I do, and entire internet does : coal cracking into fuel leads to power losses. And I'm sure it's not coincidence - Wube devs are really smart and watch for such things.
But, obviously, you didn't read second half of my math. Coal cracking allows to optimise chemical processing and to gain significant power benefit. And that makes Wube devs double smart

[bobucles]

I think I see where you're coming from. Don't crack the light oil. Cracking causes you to "lose" the solid fuel value from it. Instead keep the petrol from both processes and use the solid fuel as a freebie.

In any event the techs are still presented out of order. Coal cracking provides a simple petrol boost and a switch to solid fuel, while light cracking gives the option to cut solid fuel completely from production. Coal cracking shows up around the same time that Uranium energy is getting started, so the tech process is:
- Get a first dose of solid fuel
- Obsolete solid fuel with cracking
- Shut down Light cracking and use solid fuel again with coal cracking
- Obsolete it for good with nuclear.

I dunno how many times you want to switch your factory back and forth but it's probably simpler to skip the coal fuel step entirely.

[astroshak]

Its not energy efficient to crack coal to oil for power generation.

However, it is energy efficient enough that you can do it at a remote outpost where you’re generating plastic with nothing but coal and water. This would create more pollution at the outpost though, than I’m sure people want.

[JimBarracus]

Liquifying coal is good, when you are low on oil, which is relativly common with the map generation now.
Especially midgame when you lack the capacity to do massive explorations to find more oil.

There is also plenty of coal on the map and liquyfying it is a good way to get rid of unwanted coal patches.

[Ace_W]

Liquifying coal is good, when you are low on oil, which is relativly common with the map generation now.
Especially midgame when you lack the capacity to do massive explorations to find more oil.

There is also plenty of coal on the map and liquyfying it is a good way to get rid of unwanted coal patches.

Especially after you switch to solar power. Coal becomes a nuisance resource. So you either store it, or find ways to "burn" it.

[GrumpyJoe]

Especially after you switch to solar power. Coal becomes a nuisance resource. So you either store it, or find ways to "burn" it.

I put it in grenades, which i put into the biggest enemy in factorio: trees!

[Pentium100]

It looks like some update changed this to where coal -> solid fuel conversion produces energy.

I tested using this setup:

screenshot-tick-25341879.png (4.04 MiB) Viewed 9429 times

All electricity is produced locally. I used 300 units of coal and two heavy oil barrels (to have enough heavy oil to start the process). No modules.

To start, I had to put 20 units of coal in the "output box" so that there would be electricity and steam for the coal liquefication process, that left 280 units in the "input box".

After the process ended, there was 163 units of solid fuel in the "output box" (not counting the fuel that is in the boilers or the inserters). 163 units of solid fuel are equivalent to 489 units of coal. Since I started with 300 units, the energy efficiency is 163%.

I probably could optimize this by using electric inserters and modules, but I just wanted to try it out to see if it is possible to gain energy by doing this.

[astroshak]

It looks like some update changed this to where coal -> solid fuel conversion produces energy.

I tested using this setup:
screenshot-tick-25341879.png

All electricity is produced locally. I used 300 units of coal and two heavy oil barrels (to have enough heavy oil to start the process). No modules.

To start, I had to put 20 units of coal in the "output box" so that there would be electricity and steam for the coal liquefication process, that left 280 units in the "input box".

After the process ended, there was 163 units of solid fuel in the "output box" (not counting the fuel that is in the boilers or the inserters). 163 units of solid fuel are equivalent to 489 units of coal. Since I started with 300 units, the energy efficiency is 163%.

I probably could optimize this by using electric inserters and modules, but I just wanted to try it out to see if it is possible to gain energy by doing this.

It’s ok but you might like this thread :
viewtopic.php?f=5&t=71823

[Koub]

It’s ok but you might like this thread :
viewtopic.php?f=5&t=71823

Bear in mind that that thread was created during 0.17, and on top of that before the minor release that completely changed oil industry.

[astroshak]

That’s true enough. And my sentence should have read “Its old but” rather than what my phone corrected it to, that I’d not noticed until now...

[Moo Rhy]

Base case:
With 2 mining drills we mine 1 coal/s to put into our burners. The coal gives us 4 MW but the drills need 180 kW. This gives us a net power output of 3.82 MW.

First without modules:
1 solid fuel per second equals 12 MW. But the production consumes 1.08 MW of electrical power and we must burn a bit of the solid fuel to make steam. This gives us a net power of 10.92 MW. Divided by the 1.379/s coal we initially mined we can say that 1 coal/s transformed into solid fuel gives us 7.919 MW of power.
We already doubled the efficiency.

factorio_coal_solidfuel.png (89.51 KiB) Viewed 9260 times

With modules:
Net power output of 10.48 MW per coal piece. 2.74 times the intial efficiency.

factorio_coal_solidfuel2.png (120.21 KiB) Viewed 9260 times

https://kirkmcdonald.github.io/calc.htm ... 6e9viLfa83

[starlinvf]

Since people are doing math..... how much energy is wasted using a heat exchanger vs a boiler for the cracking process? I'm curious, because I usually do this for Rocket fuel production in late game, so I don't have to retool oil production on the research side. Just set up a dedicated heat exchanger for steam (tapped off the power plant), and convert everything into rocket fuel.